Nutritional infertility: the role of the interconnected hypothalamic neuropeptide Y-galanin-opioid network

Neuropeptide Y (NPY) has been implicated in the hypothalamic regulation of reproduction and energy homeostasis. The perikarya located primarily in the arcuate nucleus (ARC) of the hypothalamus constitute a common source of NPY. Projections from these neurons along two distinct pathways, namely, the reproductive axis of the ARC--median eminence--medial preoptic area and the orexigenic axis of the ARC--paraventricular nucleus and neighboring regions, participate in regulation of these two neuroendocrine functions. Additionally, the NPY neuronal system within the basal hypothalamus is morphologically and functionally linked with galanin and the opioid networks which also play roles in the control of reproduction and ingestive behavior. Recent experimental evidence indicates that genetic, hormonal, and environmental factors that cause nutritional imbalance and metabolic disturbances, along with depressed pituitary gonadal function, produce alterations in the synthesis, storage, and release of NPY and in other connected peptidergic systems in the hypothalamus. The current findings summarized in this review support our concept that NPY may-be one of the essential messenger molecules that serve as a communication bridge between the neural processes that regulate reproduction and those that maintain energy homeostasis. Modification in information flow within this peptidergic network due to nutritional imbalance may adversely impact hypothalamo-pituitary-gonadal function.